All it means is the DAC can play very high resolution files. Not much benefit if you listen to full size headphones or IEMs as it is hard to tell the difference between FLAC and 320kbs mp3. Do a search for gregorio's thread called 24bit vs 16bit the myth explained. In your collection you don't have any 24bit high resolution files so you wouldn't be seeing the 'benefit' of a 24/192 DAC but it would still work with your mp3s.

Let's go a little bit further with this. The 128/320/bigger number is not either of the numbers referenced on the DAC. That number is just an expression of how big the file is for how long it is. With lossy compression, this is set as a target, and the quality of the compression is dependent on how much space you're willing to consume. With your FLAC files, which are lossless, it merely indicates how efficiently it managed to compress it. But it's not a quality issue, lossless is lossless.

The two numbers are your bit depth (24) and your sample rate (192). Imagine an image of a sine wave running horizontally. To recreate that in PCM, we slice it up into a number of slices - samples - horizontally. The more slices we have (sample rate), the closer we (theoretically) come to that curve. Each slice has its position vertically as well. That's the bit depth, representing (again, theoretically) potential dynamic range.

So, of the files you mentioned, the FLACs are the only ones that this may have an impact on. And to find out, you need to pull up properties, or whatever, on them, and look for those two factors. Most will almost certainly be 16/44.1 - this is what's on a CD. Anything from high-res download sites, or ripped from SACDs will be higher, and if you want your DAC to reproduce it without any resampling, your DAC should be able to match up.

This is all grossly oversimplified, and ignores whether or not these differences actually have a practical impact upon listening. If most of your library is MP3 anyway, that's the least of your worries. Even if that isn't true... just worry about getting a DAC that sounds good, and not whose got the biggest numbers.